Field of the Invention
The field of the invention relates to an apparatus and method for producing an orbital movement in a plane, particularly for shaking and/or rotating a fluid sample.
Brief Description of the Related Art
Existing systems are known for creating an orbital shaking movement for ensuring that particles in fluids in sample holders do not settle down at the bottom of a container forming the sample holder.
Existing systems are also known that use a belt for driving one or more pulleys and having two shafts. A first one of the shafts is coaxial to the main axis of the pulley and is located on one of the flat sides of the pulley. A second one of the shafts is located on an opposite flat side of the pulley with an offset to the main axis. These pulleys are mounted with a coaxial shaft in a structure, which does not orbit, and with the other shafts in an orbiting structure, which orbits when a drive motor drives the belt. The orbiting structure can be attached to or be part of a platform on which the sample holders can be placed. These prior art systems often have two or more eccentric shaft pulleys to support the weight of the sample holders including the fluid samples.
The prior art systems often include a counterweight to balance the orbiting mass. The center of counterweight needs to be aligned at 180° to the center of gravity of the orbiting parts. A mechanism or method is needed to ensure alignment of the rotation angles of the pulleys and the counterweight.
The sample holders of the prior art need to be moved to a so-called pipetting position reachable by a pipettor to be filled or emptied. The structure with the sample holders is rotated by a second motor to move the sample holder for filling or emptying to the pipetting position. In an alternative manner, the sample holders can be placed on a rectangular plate for positioning the sample holders to the pipetting position with a second motor moving the rectangular plate in an X- and Y-direction.
Another system is known which uses a planetary drive with round holders for the sample holders. The planetary drive comprises a plurality of small gear wheels, which orbit around a larger gear wheel. The orbiting movement of the gear wheels and the movement of the sample holders into the pipetting position is carried out by the same motor. The motor turns the supporting structure carrying the sample holders on its upper surface and the corresponding small gear wheels on the lower surface in a manner such that the fluid holders and the gear wheels can rotate about a common axis. The small gear wheels engage with a fixed center wheel. The sample holders turn about their own axis and orbit the center wheel at the same time when the planetary drive is in operation. Thus, the fluid in the sample holders is moved sufficiently to prevent particles from settling down at the bottom of the sample holder. The sample holders can be placed in the required pipetting position.
It is known that the belts of the prior art systems are prone to failure from elongation and excessive wear over time. This problem can be aggregated in high temperature environments. The belt drive systems and the planetary drive systems of the prior art also require a certain amount of space for their operation. In particular, the planetary drive system requires a separate holder for each one of the sample holders. Thus, there is a limitation on the maximum number of sample holders that can be placed on the system or the required space may be too large in order to enable high performance system specifications. It is also known that belt drives require more maintenance in general than the gear wheel drives. The belt drives can also be more difficult and time-consuming to assemble. There is also a risk of wrong assembly.
One of the further issues associated with the planetary drive is that it does not allow positioning of the sample holders without shaking the fluids in the sample holders and this can lead to difficulties with pipetting in a short time frame.